A　high-power　single-frequency,　single-polarization,　thuliumdoped　all-fiber　master-oscillator　power-amplifier　(MOPA)　is　demonstrated　by　using　all-polarization-maintaining　(all-PM)　thulium-doped　fiber　and　all-PM-fiber　components.　The　MOPA　yielded　210　W　of　single-frequency,　linear-polarized　laser　output　at　central　wavelength　of　2000.9　nm　with　a　polarization　extinction　ratio　(PER)　of　＞17　dB.　No　indication　of　stimulated　Brillouin　scattering　(SBS)　could　be　observed　at　the　highest　output　power　level,　and　the　output　power　was　only　currently　limited　by　available　pump　power.　To　the　best　of　our　knowledge,　this　is　the　first　demonstration　of　average　output　power　exceeding　200　W　from　a　single-frequency,　single-polarization,　thulium-doped　all-fiber　laser　at　2　mu　m　wavelength　region.　(C)2014　Optical　Society　of　America